System to control daylight and artificial illumination and sun glare in a space

ABSTRACT

An illumination maintenance system for maintaining a desired illumination profile in a space throughout at least a portion of a day where the illumination sources include daylight and artificial light, the system comprising a first sensor for sensing an illumination level in at least a portion of the space, at least one window treatment for at least one opening for allowing daylight into the space, the window treatment selectively altering the amount of daylight entering the space, a plurality of electric lamps providing artificial light to supplement the daylight illumination of the space; the electric lamps being dimmable, a control system controlling the at least one window treatment and the plurality of electric lamps to maintain the desired illumination profile in the space, the control system controlling the plurality of electric lamps so that the dimming level of each lamp is adjusted to achieve the desired lighting profile and compensate for the daylight illumination in the space throughout at least the portion of the day; and the control system further operating to adjust the window treatment in the event of sun glare through the opening to reduce the sun glare and such that when the desired illumination profile within a defined tolerance is achieved, the control system stops varying the dimming levels of the lamps and the adjustment of the at least one window treatment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit and priority of U.S. Provisionalapplication Ser. No. 60/457,276 filed Mar. 24, 2003 entitled “Multi-ZoneClosed Loop Illumination Maintenance System” and U.S. Provisionalapplication Ser. No. 60/529,996 filed Dec. 15, 2003 entitled “System ToControl Daylight and Artificial Illumination and Sun Glare in a Space”and is related to U.S. application Ser. No. 10/660,061 filed Sep. 11,2003, entitled “MOTORIZED WINDOW SHADE CONTROL” and U.S. Pat. No.4,236,101 granted Nov. 25, 1980 entitled “Light Control System” theentire disclosures of which are hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a system to provide sufficient andcomfortable lighting within a space. In particular, the inventionrelates to a system for the automatic control of the light levels in aspace by the control of the intensity of electric lighting and/ordaylight in a space. In particular, in one embodiment, the presentinvention is directed to the control of the lighting level in a space,such as an interior room, by controlling both the artificial light inthe space by control of the intensity of electric lighting in the spaceand the control of motorized window treatments in the space in order toachieve a reasonably constant illumination on task surfaces throughoutthe space. In addition, the invention is directed to a system to reduceor prevent sun glare, which can potentially occur at low sun angles dueto sunshine through windows or other openings, e.g., skylights,surrounding the space. Such a condition is likely to occur at or nearsunset or sunrise.

Further, the invention is directed to the control of electric lightingin a space in multiple zones of the space to achieve a preset lightingprofile in the space. A “lighting profile” represents a desireddistribution of target illumination values in various portions of thespace. Additionally, the invention is directed to the control of windowtreatments such as shades based on light levels in the interior of thespace so as to maintain a predefined illumination profile in the spaceand/or to minimize or eliminate sun glare through openings into thespace. Further, the invention is directed to a system which performs thethree functions of controlling electric lighting in the space,controlling natural lighting in the space in order to achieve apredefined illumination profile and minimizing or eliminating sun glareinto the pace. The invention is thus directed to an illuminationmaintenance system for achieving a predefined illumination profile in aspace where the light is provided by natural light or artificial lightor both and further where sun glare is optionally minimized oreliminated.

One of the major problems of illumination maintenance systems, and inparticular, closed loop (feedback) illumination maintenance systems, isthe variation of incident light at the sensor or sensors employed fordetecting the incident light due to occupants moving in the space orsome other type of variation of surface reflections in the space. One ofthe prior art approaches to solve this problem is to average theillumination readings from multiple light level sensors. Anotherapproach is to position or orient the field of view of the sensors suchthat the sensors are not influenced by the occupant traffic or othershort or long term variations of the optical properties of theenvironment.

Further, open loop systems have been developed for illuminationmaintenance and daylight harvesting but such open loop systems are notsuitable for window treatment control implemented based on the interiorlight sensors because when a shading or window treatment device isclosed, access to exterior lighting conditions is prevented orrestricted.

Currently available commercial solutions for daylight control of windowtreatments are mostly based on exterior light sensors and predictivecontrol algorithms. Exterior light sensors cause maintenance problemsand require exterior wiring. Predictive control schemes are difficult toconfigure. Usually a long process of measurements and computer ormechanical model simulations must be performed before the control systemcan be correctly configured.

Further, a conventional approach that attempts to solve the glareproblem due to sunshine entering through windows at a low sun angleutilizes some form of open loop control of window treatments. In thesesystems, the algorithms are usually based on the use of exteriorphotosensors. These conventional systems employ a combination ofstrategies based on the exterior light level readings and a time clockin order to derive the required shade positions. A study of the expectedlighting conditions is regularly performed in order to predict the timeswhen the glare incidents are likely to occur. Some of the problems withthis type of control are that it demands maintenance of exterior photosensors exposed to the elements and there are problems with wiringand/or mounting sensors continuously exposed to the outside lightingconditions. Furthermore, preparation and creation of complex databasesis required to define the lighting conditions for each space of abuilding throughout a year for large buildings, which is time consumingand expensive. Further, these systems require control databasemodifications in case exterior shading objects are added such as newbuildings or plants and further, the controls cannot be fully optimizedfor each space of a large building and therefore do not result inoptimal occupant comfort and energy savings.

SUMMARY OF THE INVENTION

The present invention provides a new approach to maintenance ofillumination in a confined space where the sources of the illuminationinclude combinations of daylight and electric lamps in the space. Thespace may be divided into illumination zones. The new approach allowsfor variable and flexible daylight compensation without using separatesensing for each illumination zone and for integrated control of windowtreatments. One or more sensors can be used to control a plurality ofelectric lamps in order to reasonably and accurately maintain a desiredillumination profile in the space. In addition, a plurality of lightsensors can be used to produce a control variable corresponding to thecurrent overall illumination. This approach results in the ability toaccurately control local illumination without requiring localizedsensing for different parts of the space.

A further advantage of the present invention is that the overallillumination in the space can be maintained for multiple lightingprofiles. Each of these lighting profiles can have differentrequirements for the overall illumination and the relations ofilluminations in different portions of the space.

Two exemplary embodiments for the electric light control implementationare described herein, although variations of these embodiments will beapparent to those of skill in the art based on the descriptionscontained herein. These embodiments may employ control options definedas “open loop” control and “closed loop” control. The term “open loop”is used to describe an electric light control system based on signalsfrom interior light sensors that predominantly sense daylight enteringthe space. The term “closed loop” refers to electric light level controlsystems using interior light sensors which predominantly sense acombination of daylight entering the space and the light generated bythe electric light sources being controlled.

The invention also describes a closed loop system for control of windowshading devices. It is assumed that such closed loop system isimplemented based on the light readings from a light sensor sensingdominantly daylight entering the space through the windows affected bythe window treatments being controlled. Therefore the sensor incidentillumination changes as a consequence of window treatment adjustment.

Based on one embodiment of the present invention the control of both theplurality of electric lights and window treatments can be achieved usingonly a single photosensor or a single averaged reading from a pluralityof interior sensors. Thus the single signal (single input variable) froma single light sensor or group of light sensors can be used as an inputfor a closed loop algorithm for control of window treatments and an openloop algorithm for control of electric lights.

As discussed above, one of the problems with prior art systems is thatexterior light sensors and predictive control algorithms are employedfor control of window treatments. As described above, these systemsrequire maintenance of exterior sensors and complex data gathering andsetup procedures. The control approach of the present inventioneliminates the need for exterior sensors and these data gathering andsetup procedures, thus reducing the overall system cost.

In addition, the present invention also allows sun glare in the interiorspace to be controlled. The present invention can provide near optimalillumination control of the space. Furthermore, the properties of thespace such as the aperture ratios or openings, geometric orientation ofthe windows or exterior shading objects do not need to be known prior tothe installation and commissioning of the system. Both illumination andglare can be controlled without significantly sacrificing energy savingsresulting from the use of daylight or interior illumination. The systemhas the potential to automatically recalibrate based on immediate orrepeated occupant input resulting in increased occupant satisfaction.

Another object of the invention is to maximize daylight savings byclosing the window treatment only during glare incidents and duringtimes when the sunlight illumination near windows exceeds a presetcalibration value.

In this application, it should be understood that “windows” refers toany openings into a space including, e.g., skylights or any otheropenings. Further, “window treatment” refer to any type of openingshading device, such as blinds, shades, controllable or glazing or anyother device whose purpose is to control the amount of light entering orleaving the space through an opening of any kind, whether in a buildingwall or roof.

According to one aspect, the invention comprises an illuminationmaintenance system for maintaining a desired illumination profile in aspace throughout at least a portion of a day where the illuminationsources include daylight and artificial light, the system comprising asensor for sensing an illumination level in at least a portion of thespace, a plurality of electric lamps providing artificial light tosupplement the daylight illumination of the space; the electric lampsbeing dimmable and being arranged in one or more zones in the space, thezones defining predefined volumes of the space, each zone having atleast one lamp, a control system controlling the dimming levels of theplurality of electric lamps to maintain the desired illumination profilein the space, the at least one lamp of each zone being controlled to adimming level to achieve a desired illumination level in the respectivezone according to the desired illumination profile, the control systemcontrolling the plurality of electric lamps so that the dimming level ofeach lamp is adjusted to achieve the desired illumination profile andcompensate for the daylight illumination in the space throughout atleast the portion of the day, wherein the dimming level of each lamp isselected by the control system from one of a plurality of lightingpresets, each preset comprising a combination of dimming levels of thelamps and wherein the control system fades the electric lamps toward apreset that will result in an appropriate supplementing of the daylightillumination to achieve the desired illumination profile in the space;and the control system operating such that, when the desiredillumination profile is achieved within a predefined tolerance, thecontrol system stops varying the dimming levels of the lamps.

According to another aspect, the invention comprises an illuminationmaintenance system for maintaining a desired illumination profile in aspace throughout at least a portion of a day where the illuminationsource comprises daylight entering the space, the system comprising asensor for sensing an illumination level in at least a portion of thespace, at least one electrically controllable window treatment for atleast one opening for allowing daylight into the space, the windowtreatment selectively altering the amount of daylight entering the spacethrough the opening, a control system controlling the at least onewindow treatment, the control system controlling the at least one windowtreatment to achieve the desired illumination profile in the spacethroughout at least the portion of the day, and wherein the controlsystem stops adjusting the at least one window treatment when thedesired illumination profile within a predefined tolerance has beenachieved.

According to a further aspect, the invention comprises a system forreducing sun glare through an opening into a space, the systemcomprising at least one electrically controllable window treatment forat least one opening for allowing daylight into the space, the windowtreatment selectively altering the amount of daylight entering the spacethrough the opening, a sensor for sensing daylight illumination enteringthe space, a control system controlling the at least one windowtreatment, and the control system operating to adjust the windowtreatment in the event of sun glare through the opening to reduce thesun glare, and such that when the sun glare has been minimized, thecontrol system stops the adjustment of the at least one windowtreatment.

According to yet another aspect, the invention comprises an illuminationmaintenance system for maintaining a desired illumination profile in aspace throughout at least a portion of a day where the illuminationsource comprises daylight entering the space, the system comprising atleast one electrically controllable window treatment for at least oneopening for allowing daylight into the space, the window treatmentselectively altering the amount of daylight entering the space throughthe opening, a sensor for sensing daylight illumination entering thespace, a control system controlling the at least one window treatment tomaintain the desired illumination profile in the space throughout atleast the portion of the day, and the control system further operatingto adjust the window treatment in the event of sun glare through theopening to reduce the sun glare, and such that when the desiredillumination profile within a predefined tolerance is achieved, thecontrol system stops the adjustment of the at least one windowtreatment.

According to still another aspect, the invention comprises anillumination maintenance system for maintaining a desired illuminationprofile in a space throughout at least a portion of a day where theillumination sources include daylight and artificial light, the systemcomprising a first sensor for sensing an illumination level in at leasta portion of the space, at least one electrically controllable windowtreatment for at least one opening for allowing daylight into the space,the window treatment selectively altering the amount of daylightentering the space through the opening, a plurality of electric lampsproviding artificial light to supplement the daylight illumination ofthe space, the electric lamps being dimmable, a control systemcontrolling the at least one window treatment and the plurality ofelectric lamps to maintain the desired illumination profile in thespace, the control system controlling the plurality of electric lamps sothat the dimming level of each lamp is adjusted to achieve the desiredillumination profile and compensate for the daylight illumination in thespace throughout at least the portion of the day, and the control systemfurther operating to adjust the at least one window treatment in theevent of sun glare through the opening to reduce the sun glare, and suchthat when the glare is eliminated or reduced to a satisfactory level andthe desired illumination profile within a predefined tolerance isachieved, the control system stops varying the dimming levels of thelamps and the adjustment of the window treatment.

According to a further embodiment of the invention, the illuminationmaintenance system for an interior space comprises a sensor for sensingillumination in one portion of the space or alternatively for sensing ofaverage illumination in the space, a lighting source to supplementdaylight illumination comprising multiple independently controllabledimmable electric lights, and optionally electrically controllablewindow and/or skylight shading devices to attenuate daylightillumination, for example roller shades, any type of blind orelectrically controllable window or skylight glazing.

According to yet another embodiment, the invention comprises anillumination maintenance system for maintaining a desired illuminationprofile in a space throughout at least a portion of a day where theillumination sources include daylight and artificial light, the systemcomprising at least one interior sensor for sensing an illuminationlevel in at least a portion of the space; at least one electricallycontrollable window treatment for at least one opening for allowingdaylight into the space, the window treatment selectively altering theamount of daylight entering the space through the opening; a pluralityof electric lamps providing artificial light to supplement the daylightillumination of the space, the electric lamps being dimmable; a controlsystem controlling the at least one window treatment and the pluralityof electric lamps to maintain the desired illumination profile in thespace; the control system controlling the plurality of electric lamps sothat the dimming level of each lamp is adjusted to achieve the desiredillumination profile and compensate for the daylight illumination in thespace throughout at least a portion of the day; wherein the control ofthe electric lamps is implemented based on an open loop controlalgorithm and the control of window shading devices is implemented basedon a closed loop control algorithm; and wherein the control of both theelectric lamps and the window treatments is based on a signalrepresenting a single input variable derived from the at least oneinterior sensor.

Further, the system comprises an automatic control system operating boththe window and/or skylight shading devices and the electric lights inorder to maintain a desired illumination profile in the space.

According to a first electric light control method of the invention, theelectric lights are controlled using a closed loop algorithm.Preferably, the lighting control system operates the electric lights sothat the lights are dimmed between two or more fixed presets or scenes.Each preset comprises a combination of dimming levels to achieve thedesired lighting profile and compensate for the daylight availability inthe space through the day. The presets are ordered based either on theoverall dimming level for each zone or the dimming levels intended forparticular portions of the space. The correlation of dimming level ofthe individual lighting zones for each preset is set in the inverseproportion to the daylight available at a particular position in thespace.

The control system automatically adjusts the dimming level of theelectric lights towards a preset that would result in the appropriatesupplementing of the available daylight. When the desired illuminationis achieved, the system stops varying the light output from the electriclights and/or stops varying the position or transparency of the shadingdevices. The system adjusts a plurality of electric lights betweenpresets corresponding to one or more daytime lighting conditions and anighttime lighting condition. Both the window shading devices and theelectric lights can be controlled using one or more interiorphotosensors representing a single input to the control system.Alternatively, the window shading devices can be controlled based uponone or more interior photosensors separate from the photosensors used tocontrol the electric lights and connected to a lighting controlprocessor.

The method for control of window treatments described by the presentinvention can also be combined with an open loop method for control ofelectric lights. This open loop method for electric light control canpreferably be implemented as described in the referenced U.S. Pat. No.4,236,101, the entire disclosure of which is incorporated by referenceherein.

In the case when an independent second photosensor or a set ofphotosensors are used for the control of the window shading devices, thephoto sensors are preferably mounted close to the window such that theirfield of view is oriented toward the windows such that they dominantlysense the daylight entering the space.

As mentioned, an independent set of photosensors can be used for thecontrol of electric lights. These sensors can be of the same type as thephotosensors controlling the window shading device and are in anexemplary embodiment connected to the lighting control system via aseparate interface unit. The light level readings from these sensors areprocessed by an independent control algorithm. The photosensors used forthe electric light control are preferably mounted at approximately twowindow heights away from the windows. In one particular implementation,the sensors are oriented so that their field of view is away from thewindows. This orientation is suitable for a closed loop lighting controlsystem. However, dominantly open loop system could also be employed forthis purpose. In the case of dominantly open loop control, the field ofview of the interior sensors for the electric lighting control isoriented towards the windows.

The invention also comprises methods for illumination maintenance.

According to one aspect, the invention comprises a method formaintaining a desired illumination profile in a space throughout atleast a portion of a day where the illumination sources include daylightand artificial light, the method comprising sensing an illuminationlevel in at least a portion of the space, supplementing the daylightillumination of the space with a plurality of electric lamps providingartificial light, the electric lamps being dimmable and being arrangedin one or more zones in the space, the zones defining predefined volumesof the space, each zone having at least one lamp, controlling with acontrol system responsive to the sensed illumination level the dimminglevels of the plurality of electric lamps to maintain the desiredillumination profile in the space, the step of controlling comprisingadjusting the dimming level of the at least one lamp of each zone toachieve a desired illumination level in the respective zone and therebymaintain the desired illumination profile in the space and compensatefor the daylight illumination in the space, wherein the dimming level ofeach lamp is selected by the control system from one of a plurality oflighting presets, each preset comprising a combination of dimming levelsof the lamps and wherein the control system fades the electric lampstoward a preset that will result in an appropriate supplementing of thedaylight illumination to achieve the desired illumination profile in thespace; stopping varying of the dimming levels of the lamps when thedesired illumination profile within a predefined tolerance is achieved,and repeating the above steps during the day to maintain the desiredillumination profile throughout at least the portion of the day.

According to another aspect the invention comprises a method formaintaining a desired illumination profile in a space throughout atleast a portion of a day where the illumination source comprisesdaylight entering the space, the method comprising, sensing anillumination level in at least a portion of the space, providing atleast one electrically controllable window treatment for at least oneopening for allowing daylight into the space, the window treatmentselectively altering the amount of daylight entering the space throughthe opening, controlling the at least one window treatment with acontrol system responsive to the sensed illumination level to achievethe desired illumination profile in the space, stopping adjusting the atleast one window treatment with the control system when the desiredillumination profile within a predefined tolerance has been achieved,and repeating the above steps during the day to maintain the desiredillumination profile throughout at least the portion of the day.

According to yet another aspect, the invention comprises a method forreducing sun glare through an opening into a space, the methodcomprising, providing at least one electrically controllable windowtreatment for at least one opening for allowing daylight into the space,the window treatment selectively altering the amount of daylightentering the space through the opening, sensing daylight illuminationentering the space, controlling with a control system responsive to thesensed daylight illumination the at least one window treatment, andadjusting with the control system the window treatment in the event ofsun glare through the opening to reduce the sun glare, and when the sunglare has been minimized, stopping adjustment of the at least one windowtreatment.

According to still yet another aspect, the invention comprises a methodfor maintaining a desired illumination profile in a space throughout atleast a portion of a day where the illumination source comprisesdaylight entering the space, the method comprising, providing at leastone electrically controllable window treatment for at least one openingfor allowing daylight into the space, the window treatment selectivelyaltering the amount of daylight entering the space through the opening,sensing daylight illumination entering the space, controlling with acontrol system responsive to the sensed daylight illumination the atleast one window treatment to maintain the desired illumination profilein the space throughout at least the portion of the day, and furtheradjusting with the control system the window treatment in the event ofsun glare through the opening to reduce the sun glare, and when thedesired illumination profile within a predefined tolerance is achieved,stopping adjustment of the at least one window treatment, furthercomprising repeating the above steps during the day to maintain thedesired illumination profile throughout at least the portion of the day.

Yet another aspect of the invention comprises a method for maintaining adesired illumination profile in a space throughout at least a portion ofa day where the illumination sources include daylight and artificiallight, the method comprising, sensing an illumination level in at leasta portion of the space, providing at least one electrically controllablewindow treatment for at least one opening for allowing daylight into thespace, the window treatment selectively altering the amount of daylightentering the space through the opening, supplementing the daylightillumination of the space with a plurality of electric lamps providingartificial light, the electric lamps being dimmable, controlling with acontrol system responsive to the sensed illumination level the at leastone window treatment and the plurality of electric lamps to maintain thedesired illumination profile in the space, controlling with the controlsystem the plurality of electric lamps so that the dimming level of eachlamp is adjusted to achieve the desired illumination profile andcompensate for the daylight illumination in the space throughout atleast the portion of the day, further adjusting with the control systemthe at least one window treatment in the event of sun glare through theopening to reduce the sun glare, stopping varying of the dimming levelsof the lamps and the adjustment of the window treatment when the desiredillumination profile within a predefined tolerance is achieved, andrepeating the above steps during the day to maintain the desiredillumination profile throughout at least the portion of the day.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail in the followingdetailed description with reference to the drawings in which:

FIG. 1 is a block diagram of a lighting maintenance system according tothe invention;

FIG. 2 shows the floor plan of a typical room layout with the system ofthe invention connected to the various sensors, lighting sources andcontrollable window treatments;

FIG. 3 is a diagram showing a first example of a preset configurationfor a flat lighting profile;

FIG. 4 shows a second example of a preset configuration for a differentlighting profile;

FIG. 5 shows a third example of a preset configuration for yet adifferent lighting profile;

FIG. 6 shows a process flow of the system main loop;

FIG. 7 a shows the process flow for a first system controlling theelectric lamps only, when the lighting in the space is too dark;

FIG. 7 b shows the process flow for the first system controlling theelectric lamps only, when the lighting in the space is acceptable;

FIG. 7 c shows the process flow for the first system controlling theelectric lamps only, when the lighting conditions in the interior spaceare that there is too much light;

FIG. 8 a show the process flow for a second system controlling bothelectric lamps and window treatments, when the lighting is too dark;

FIG. 8 b shows the process flow for the second system when the lightingis acceptable;

FIG. 8 c show the process flow for the second system when there is toomuch light;

FIG. 9 is the process flow of the system showing how the system varies atime delay to operate the window treatments in response to the amount ofillumination;

FIG. 10 shows how the system varies the dead-band set point to reduceglare;

FIG. 11 shows an alternative process flow for reducing sun glare;

FIG. 12 shows the process flow in response to a manual override;

FIG. 13, comprising FIGS. 13 a and 13 b, shows how sun angle ismeasured; and

FIG. 14 shows graphs of illumination levels and when glare control isneeded throughout a day.

DETAILED DESCRIPTION OF THE INVENTION

With reference now to the drawings, FIG. 1 is a block diagram of anembodiment of the invention for controlling the illumination levels in aspace such as a room, where both daylight and artificial lighting act aslight sources, as well as for reducing sun glare. The system 10comprises a central processor 100 which may be a Lutron GRAFIK 6000®central lighting processor, for example, Model No. GR6MXINP. The centralprocessor 100 has coupled thereto a dimming panel 110 which has variouslighting loads 120 which can be any light source type including but notlimited to incandescent, fluorescent, HID (High Intensity Discharge),neon, LED (Light Emitting Diode), LV (Low Voltage) coupled thereto andwhich are controlled by the dimming panel 110 in response to commandsfrom the central processor 100 communicated via a digital communicationlink 137. The dimming panel may be a Lutron type GP12-1203ML-15.Photosensor interface 130 is coupled to the central processor via adigital communication link 135. Coupled to the photosensor interface 130are one or more photosensors 140 which may be microWATT® photosensorsavailable from Lutron model No. MW-PS-WH. Photosensors 140 are forcontrol of the interior lights 120. A further photosensor interface 132is coupled to the central processor 100 via the link 135. Coupled to thephotosensor interface 132 are one or more photosensors 145 which may bemicroWATT photosensors available from Lutron model No. MW-PS-WH.Photosensors 145 are for control of the motorized window treatments 170.

One or more wall stations 150 may be provided which are coupled to thecentral processor 100 as well as the photosensor interfaces via thedigital communication link 135. These wall stations 150 are provided formanual control of the various lighting loads 120. Also connected to thelink 135 may be a window treatment controller 160 for manuallycontrolling the window treatments 170. This controller 160 may be aLutron GRAFIK 6000 Sivoia® controller model No. SO-SVCI-WH-EO1. Windowtreatments 170 may comprise Lutron Sivoia motor drive units, e.g., modelNo. SV-MDU-20 or Lutron Sivoia QED™ electronic drive units, e.g. modelNo. SVQ-EDU-20 driving Lutron Sivoia roller shades, Kit no. SV-RS-KIT.

A computer, for example a personal computer 180 may be coupled to thecentral processor 100 via an interface adapter 190 and suitableconnections such as a PC jack 200 for programming/monitoring of thecentral processor. Note that a Lutron GRAFIK 7000™ central lightingprocessor could be used in place of the GRAFIK 6000 central processor.

FIG. 2 shows a floor plan of a typical room layout. The centralprocessor 100 and dimming panel 110 are shown located in an electricalcloset. The various lamps 120 are also shown and are grouped into, forexample, five zones, each zone controlled separately by the dimmingpanel. Zone 1 is closest to the windows 172. A different number of zonescan be employed, including a single zone. The photosensor interface 130is coupled to the photosensors 140 and the interface 130 is connected tothe central processor 100. Photosensors 140 are preferably mounted suchthat there is no or minimal daylight shining directly into thephotosensor and so that the photosensor measures the light reflected offthe surfaces in the illuminated space. Photosensors 140 are preferablymounted at approximately two window heights away from the windows 172.The window treatment controller 160 is coupled to the motorized windowtreatment motors 171 driving the window treatments 170. The windowtreatment controller 160, allows manual control of the window treatments170. The Photosensor interface 132 is coupled to a photosensor orphotosensors 145 for sensing daylight entering the room and is connectedto the central processor 100. Photosensors 145 are directed so thattheir field of view is toward the window and are preferably mountedwithin one window height of the windows 172.

The central processor 100 manages the lighting for an entire facilityand allows the user to create and recall custom preset scenes (orpresets) for common room activities, for example, general meetings,audio-video presentations, special events, etc. Scenes are set byadjusting the intensity of each zone of electric lights or motorizedwindow treatments to generate a combination for the particular activity.Wall stations 150, hand held controls, preprogrammed time clock events,occupancy sensors, and photosensors 140, 145 can supply inputs to thesystem to select any scene in any area. The central processor 100includes an astronomical time clock, which is capable of schedulingevents based on sunrise and sunset times. System design and setup areaccomplished using, e.g. Lutron GRAFIK 6000 setup software on a personalcomputer 180. When system setup is complete, the computer 180 may beused for system monitoring and real time operation. One standard centralprocessor 100 can control up to 512 zones and 544 scenes with up to 96control points.

The motorized window treatments 170 allow the system to control naturallight in addition to electric light. The motors 171 can be programmed topreset window treatment levels. The controller 160 allows for selectionof the window treatment presets from the central processor 100. Up to 64motors can be controlled for each controller 160.

The photosensor interface 130 is used for selection of preset lightingscenes and the interface 132 is used to set window treatment levels inresponse to available daylight or electric light for optimum lightlevels, energy savings, and reduced sun glare. The photosensorinterfaces 130, 132 process the light level information fromphotosensors 140, 145 and transmit this measured illumination data tothe central processor 100 via the digital communication link 135.

In a preferred implementation of the invention, the central processor100 runs two algorithms: 1) a first algorithm for the control of thewindow treatments and the second algorithm for control of the electricallights both based on the readings of photosensors 140 communicated tothe central processor 100 through photosensor interface 130.Alternatively the first algorithm for control of window treatments canbe implemented based on the readings of photosensors 145 communicated tothe central processor through photosensor interface 132. Yet anotheralternative approach is to base the operation of both control algorithmson the readings from photosensor 145 via interface 132. In this case thecontrol of the electric lights would be based on pre-existing controlalgorithms as described in U.S. Pat. No. 4,236,101 and implemented inLutron daylight compensation products such as Micro Watt, Digital MicroWatt and Radio Touch.

In the preferred implementation described, the two algorithms areoperated by the same processor. Alternatively, the two algorithms couldwork independently and be controlled by separate processors or the sameprocessor, but operating independently. For example, one system could beprovided to adjust only the shading and to reduce glare in the space. Aseparate system could be employed only to adjust electrical lightlevels. Alternatively, one system can handle all three functions,electric light control, shade control to maintain an illuminationprofile and shade control to minimize sun glare.

In order to control the electric lights according to the first aspect ofthe invention the implementation is based on a fixed number of presets,or lighting scenes, preferably four presets may be used. However, anynumber of presets can be provided, including only one. Each presetdefines a target intensity for one or more electric lighting zones, forexample, zones 1–5 shown in FIG. 2. For a system with four resets, thesepresets will be referred to as Minimum Preset, Medium Low Preset, MediumHigh Preset and Maximum Preset.

In most cases, the Minimum Preset is configured so that all electriclights are turned off and is used to maximize daylight in the space. Forspaces where daylight contribution deeper in the space is inadequate theminimum preset is configured to maintain adequate illumination underconditions of high daylight availability and with the window treatmentsfully open. This preset is preferably calibrated when there is adequatedaylight availability in the majority of the space being controlled.

The Medium Low preset normally corresponds to the required contributionof electric lights to the overall illumination when enough daylight isavailable to achieve the highest required illumination in the space inclose proximity to the windows or other openings.

The Medium High preset corresponds to the required contribution ofelectric lights when the available daylight is between the maximum andminimum amounts.

The Maximum Preset corresponds to the required illumination in the spaceby electric lights only with no daylight available.

The above is one possible way of programming the Minimum, Medium Low,Medium High and Maximum presets, but other values for these presetscould be used.

Various preset or scene configurations are shown in FIGS. 3, 4, and 5.Each chart shows the electric light and daylight levels versus distancefrom the window. The dashed lines represent the level of the electriclights, which typically get higher farther from the window. The solidline represents the level of daylight coming in through the window at aninstantaneous time in the day, which typically decreases with distancefrom the window. FIG. 3 is an example of a preset configuration for aflat lighting profile in which the Maximum Preset has all zones atmaximum intensity (constant light level is desired across the space).The zones intensities for Medium High and Medium Low presets varydepending on distance from the window, so that zones farthest from thewindow have their lamps set brighter. FIGS. 4 and 5 show presetconfigurations, in which the presets have different graph shapes fordifferent lighting profiles.

Average illumination contribution for each of the four presets mustprovide progressively higher overall illumination as detected byphotosensors 140 installed in the space. Light level information fromone or more photosensors 140 is processed by photosensor interface 130,transmitted to central processor 100, and compared to two thresholds.These thresholds correspond to:

-   1. The minimum of the acceptable range of illumination; and-   2. Target value for the illumination; and-   3. The maximum of the acceptable range of illumination.

A light level signal comparator for comparing the light level to thethresholds is preferably of a hysteretic type and can be implementedeither as a digital or an analog component. Alternatively, thecomparator function can be implemented as part of the central processor100. Preferably this comparator should be configurable so that a numberof different lighting threshold groups can be selected based on aconfiguration input.

The resulting information will correspond to the following lightingconditions:

-   1. Illumination in the area is too dark (below minimum threshold);    and-   2. Illumination in the area is acceptable (above minimum and below    maximum threshold);-   3. Illumination in the area is too bright (above maximum threshold).

Based on this information, the central processor 100 controls one ormore electric lighting zones to achieve the desired illuminationprofile. Further, as will be described in more detail below, the systempreferably will control the window shading devices to prevent sun glarebased on input from the photosensors 145.

As discussed above, in the exemplary embodiment there are four presets,Minimum, Medium Low, Medium High and Maximum. The following paragraphsdescribe the steps taken to configure these four presets.

The calibration of the presets is performed with the control algorithmsin the processor 100 disabled and the system is under manual controlonly. The Minimum Preset is configured by setting the electric lightlevels when a high level of daylight illumination is availabledominantly exceeding the desired target illumination in the space.Lighting zone intensities for the zones closer to the windows are set tooff for the Minimum Preset.

The Medium Low Preset is configured as follows: The central processor100 is disabled and set to a manual control. With the electric lightsoff, the window treatment positions are selected such that the daylightillumination in the area around the middle of the room or under thesecond row of lights for deeper spaces is at the target level.Thereafter, the levels of all electric light zones are set such that thelight level in the entire area is acceptable. This configuration is theMedium Low Preset.

To configure the Medium High Preset, the central processor 100 isdisabled and set to manual control. Medium High Preset in conjunctionwith the Medium Low Preset defines a region of linear electric lightresponse to daylight availability. This preset is adjusted such that afixed increase of lighting intensity is added to all of the zoneintensities as calibrated for the Medium Low Preset in such a way thatno zone intensity exceeds the settings for the night time zone ascalibrated in the next step. To simplify calibration the Maximum presetcan be calibrated first.

The Maximum Preset is configured by first disabling the control systemby setting it to manual control. If blackout window treatments areinstalled, the window treatments are closed fully, otherwise it ispreferable to wait until evening when there is no daylight to set themaximum preset. The levels of all zones are set such that the lightlevel of the entire area will be acceptable with no daylight through thewindow (nighttime level). This will define the Maximum Preset.

FIG. 6 shows a preferred implementation for the main loop process flowfor a system according to the invention based on the closed loop controlmethod for control of electric lights. The main loop will besubstantially the same for a system that controls only the electriclamps as it will be for a system that controls both lamps and windowtreatments. FIGS. 7 a, 7 b and 7 c describe the process flow for asystem controlling only the electric lamps. FIGS. 8 a, 8 b and 8 cdescribe the process flow for a system controlling both the electriclamps and the window treatment devices to achieve a desired illuminationprofile. FIGS. 9–14 explain the process flow for a system that seeks toreduce or eliminate sun glare. The various loops shown in FIGS. 6–8 c aswell as FIGS. 10–12 run continuously or at regular intervals.

FIG. 6 shows the flow chart for the main control loop with the threeconditions shown: too dark 500, acceptable 510, and too light 520. If itis too dark (500), flow is into FIG. 7 a beginning at A. If the level isacceptable (510), the flow is to FIG. 7 b at B and if there is too muchlight (520), the flow is to FIG. 7 c at C. For each decision in FIG. 6,the light level as sensed by photosensors 140 is compared to one of thetwo thresholds previously described.

FIG. 7 a shows the flowchart for the too dark condition (500). In moredetail, the controller first checks at 630 to determine if the system isset at the Minimum Preset. If yes, the Medium Low Preset is selected at640. If not, a check is made to determine if the system is set to theMedium Low Preset (650). If yes, a check is made to determine if theelectric lights are being faded (660), that is, still in the process ofreaching the particular preset level. If yes, an exit is made back tothe main loop (FIG. 6). If fading (dimming level change) has beencompleted, the Medium High Preset is selected (670).

If the Medium Low Preset was not set at step 680, the system checks forwhether it is set to the Medium High Preset. Fading is checked at 690,and if fading is completed, the Maximum Preset is selected at 700.

If the system is not set at the Medium High Preset (680), a check ismade to determine if it is at the Maximum Preset (710), still fading(720), done fading (730), and the Maximum Preset is selected at 740 andthen an exit is made. If the system was not at Maximum Preset at step710, the Maximum Preset is set at 750 and an exit is made. Thus, if theMaximum Preset was determined to be the system status at step 710, andif fading of the lighting at 720, 730 to the Maximum Preset does notresult in the desired illumination, the maximum preset is set at 740. Ifthe system status at step 710 was that the Maximum Preset (nor any ofthe other three presets) was selected, the system selects the maximumpreset at step 750. Thus, if selecting and fading to any of the fourpresets does not result in the desired illumination profile, the MaximumPreset is automatically selected at 750, as this is the maximumartificial lighting illumination that can be achieved.

FIG. 7 b shows the flowchart for the acceptable lighting condition. Asshown, if the illumination is in the acceptable range (as detected byeach Photosensor 140—the measurements of the photosensors 140 can beaveraged or the thresholds for each photosensor can be different), thefading is stopped and delay times reset (760) and return is made to themain loop.

FIG. 7 c shows the flowchart for the too light condition.

At 830, a determination is made if the system is at the Maximum Preset.If yes, the Medium High Preset is selected at 840 and an exit is made.

If the Maximum Preset was not set at 830, a check is made to determineif the system has been set at the Medium High Preset at 850. If so, acheck is made to determine if the lights are still fading at 860. Ifnot, the Medium Low Preset is selected at 870. If the lights are stillfading, an exit is made. Once the Medium Low Preset is set, an exit ismade.

If at step 850 the Medium High Preset was not set, a check is made todetermine if the Medium Low Preset is set at 880. If so, a check is madeat 890 to determine if the lights are still fading. If yes, an exit ismade. If not, the Minimum Preset is selected at 900 and an exit is made.

If at step 880 the Medium Low Preset was not set, a check is made at 910to determine if the system is set to the Minimum Preset. If yes, a checkis made at 920 to determine if the lights are still fading. If yes, anexit is made, if not a check is made at 930 to determine if fading iscomplete. If yes, an exit is made. If not the Minimum Preset is selectedat 940 and an exit is made.

Finally, the Minimum Preset is selected at 950 if an acceptable lightingcondition was not determined by the main loop (FIG. 6) at any otherpoint during the steps shown in FIG. 7 c.

Thus, the system operates by constantly operating in a main loop (FIG.6), leaving the main loop, depending on whether the lighting conditionis too dark or too light (FIGS. 7 a and 7 c), constantly alternatingbetween the main loop and the loops of FIGS. 7 a and 7 c while cyclingthrough the loops of FIGS. 7 a and 7 c, and once an acceptable lightingcondition is realized during the main loop at 510, stopping fading atstep 760 (FIG. 7 b). Should an acceptable lighting condition not berealized, the system defaults to the Minimum or Maximum preset,depending on whether the condition was too much light or too dark,respectively.

In order to compensate for the difference in the spectral sensitivity ofthe photosensors 140 for different types of light sources, the set pointthresholds for the electric light control process flow are preferablyvaried. Due to the narrow frequency spectrum of the light produced byfluorescent lamps, even sensors designed with human eye correctedspectral sensitivity such as the Lutron MW-PS photosensors deliver alower output signal for fluorescent lighting compared to that producedin the presence of equivalent daylight.

The set points for the electric light control process flow are adjustedbased on the output control signal. Based on experimental measurements,the MW-PS photosensors feature around 30% lower sensitivity tofluorescent lighting compared to daylight. This difference does notpresent a problem in the usual open loop applications but must becorrected in closed loop applications. The sensitivity compensation isimplemented such that the set point is proportionally scaled between 0%and −30% when the control signal for the electric lights near thewindows changes from 100% to 0%.

One possible implementation of this set point formula is as follows:

Light Set point=Daytime Set point×(1−0.003×Window Lighting ZoneIntensity in %). The constant 0.003 is derived from the known fact thatthe MW-PS Photosensor has 30% lower sensitivity to fluorescent lighting.

The set point can also be adjusted based on the time of day. Since thewindow treatments are automatically controlled, the overall variation ofthe daylight availability in the space during the day is significantlyreduced. Therefore, the spectral sensitivity compensation will onlyeffectively be required near sunset and sunrise and can be derived basedon the sun angle for a given astronomic time clock reading. Anastronomic time clock is contained within the central processor 100.

One example of the alternative method of implementing the selection ofthe “too dark” and “too light” thresholds is to transmit the currenttime of day or the Window Lighting Zone Intensity from the centralprocessor 100 to the photosensor interface 130. The photosensorinterface 130 can then make any appropriate adjustments to the setpoint, process the light level information from the photosensors 140,compare the light level information to the set point, and transmit asignal to the central processor 100 corresponding to the current lightcondition, either “too dark” or “too light”. The central processor 100can then act accordingly to either of these conditions.

The process flow for setting the electric light source levels has thusbeen described. A further process flow for controlling the windowtreatments in conjunction with the electric lights will now bedescribed.

Turning to FIG. 8 a, it is substantially the same as FIG. 7 a, with theexception that an additional set of conditions is checked at steps 610and 620. In particular, at step 610, a check is made to determine if thewindow treatments, for example, shades, are in the manual mode, that isoverridden by manual control via wallstation 150 or window treatmentcontroller 160. If yes, the manually set position is not changed and theprocess goes to step 630, previously described. The remainder of theprocess has already been described with reference to FIG. 7 a, and willnot be repeated here. Thus, the system attempts to achieve the desiredillumination profile leaving the window treatments as manually set.

If the shades are no longer in manual mode, the step 620 is performedand a check is made to determine if the shades are fully open. If yes,the process flows again to step 630, and the system attempts to achievethe desired illumination profile so as to maximize daylight (the shadesare left in the open position) and minimize electrical energy usage.

If the shades are not fully open, the system begins to open them at 625,exits to the main loop and returns to the flow of FIG. 8 a as manycycles as necessary until the shades are fully opened, as determined atstep 620, in which case the process flow is to step 630, where theelectric lamps are then controlled.

FIG. 8 b is similar to FIG. 7 b, but shows that in a system controllingwindow treatments and lamps, when the lighting is acceptable, theadjustment of the window treatment is stopped (755), the fading oflights is stopped (760), and the shades are fully opened (770, 775),maximizing the amount of daylight in the space and minimizing electricpower usage. In another embodiment, it may be desirable, using a timeclock, to either fully close or fully open the window treatments afterdusk since there is no daylight and to address other concerns such asbut not limited to privacy, aesthetic appearance of the building ornighttime light pollution.

FIG. 8 c corresponds to FIG. 7 c, except it shows the process flow for asystem controlling lights and window treatments. Similarly to FIG. 8 a,a check is made to determine if the shades are in manual mode at 810,fully closed at 820 (because there is too much light, as opposed to toomuch darkness) and begins closing the shades at 825. The remainder ofthe flow chart is similar to FIG. 8 c and need not be discussed indetail again here.

There has thus been described a first system (FIGS. 6 to 7 c) forcontrolling only the electric lights, based on whatever daylight ispresent, without adjusting window treatments and a second systemcontrolling both lights and window treatments (FIGS. 6, 8 a to 8 c). Asystem to control only the window treatments, based on the flow of FIGS.6, 8 a to 8 c, could also be provided. In such a system, the systemwould control the window treatments based on the available daylight.

Yet a further process flow of the preferred implementation describes analternative control algorithm which, in addition to controlling diffuseddaylight illumination near windows, also controls the window treatmentsto minimize or eliminate sun glare based on the readings of photosensors145 through photosensor interface 132.

In order to prevent glare when the sun is at a low angle, for example,near sunset or sunrise, the system of the invention automaticallycontrols the window treatments 170 to prevent glare. In an exemplaryembodiment, for aesthetic reasons, the window treatments 170 arepreferably controlled in such a way that only a set number of fixedstationary window treatment positions or presets is allowed. Forexample, the window treatments 170 may move between 4 to 5 fixed windowtreatment presets including fully opened and fully closed. The controlis implemented in the form of closed loop control with a dead-band. Thiscontrol is not, however, limited to a discrete control. The controlcould be continuous, as previously described, or it could have more orfewer than 4 to 5 window treatment presets.

The term “dead-band” is used to describe a range of photosensor 145incident light level readings, which are considered by the system asacceptable and for which no action is performed other than to reset thewindow treatment delay timers. This will be described below.

The system will only change the window treatment settings when theincident light level on photosensors 145 is outside of the dead-band. Inorder to reduce the frequency of window treatment movements, allcommands are delayed. Therefore, if the particular lighting condition isonly temporary, no action will take place. However, glare control is adesirable capability of the system. Therefore, the system should respondquickly when a severe glare condition exists. Longer delays can bepermitted when insufficient light is available because the electriclights in the space can compensate for the temporary low daylightavailability.

In order to address the above variable timing, i.e., delaying windowtreatment changes for temporary conditions while responding to severeglare conditions quickly, the system employs a low sampling ratenumerical integration of the light level error. When the incident lightlevel seen by the photosensors 145 is out of the range defined as thedead-band, the difference between the upper or lower limit of the bandand the actual light level is numerically accumulated. As shown in FIG.9, at 1000 and 1010, the light level is checked to determine if it ishigher than the upper limit or lower than the lower limit and thusoutside of the dead-band. If it is within the dead-band (1015), a delaytimer accumulator is reset (1017) and an exit made. If the light levelis higher than the upper limit, control is to 1020; if it is lower thanthe lower limit, control is to 1220. In either case, when the lightlevel is outside the dead band, the actual light level is numericallyaccumulated as shown at 1040 and at 1240. When the accumulated sumexceeds predefined limits, the window treatments are moved in order tobring the light level within the dead-band. The actual timing thresholdsare different depending on the sign of the error. As mentioned above,the response time for the high illumination condition is shorter thanthe response time for the low illumination condition. Time delays arereduced in case of consistently low or consistently high sunlightillumination.

In more detail, if the light level is higher than the upper limit of thedead-band, at 1020 the previous light level is compared to the lowerlimit to determine if it was previously below the lower limit. In suchcase, the difference between the upper and lower limits is adjusted at1030 to reset the lower limit. If the light level was not previouslybelow the lower limit, or after the adjustment at 1030, the differencebetween the light level and the upper limit is accumulated, therebyresulting in a delay (1040).

At 1050, the previous light level is compared to the upper limit. If theprevious light level was also above the upper limit, a shorter timingthreshold 1060 is employed. This indicates a persistent high light levelcondition. If the previous light level was not above the upper limit, alonger timing threshold 1070 is employed. As stated above, the timedelays are reduced in the case of consistently high sunlightillumination. At 1080, the accumulated difference between the lightlevel and the upper limit is checked to determine if it is greater thanthe current timing threshold set at 1060 or 1070. When the accumulateddifference exceeds the timing threshold, the shade is moved to the nextmore closed preset as indicated at 1090. At 1100, a flag is set toindicate that the previous light level was above the upper limit asdetermined at step 1050, for the next cycle.

If the light level was lower than the lower limit as indicated at 1010,a similar process flow 1220, 1230, 1240, 1250, 1260, 1270, 1280, 1290and 1300 is employed. However, in this process flow the accumulateddifference is between the light level and the lower limit. Similarly, ashorter timing threshold is used if the previous light level was belowthe lower limit (consistently low sunlight illumination). As discussedabove, the response time for consistently high or low illuminationconditions is reduced. Time delays are reduced in the case ofconsistently low or consistently high sunlight illumination. This isindicated at 1060 for the consistently high sunlight condition and at1260 for the consistently low sunlight condition.

In order to correctly address the glare control problem, the windowtreatment control process flow employs a variable control setpoint orthreshold. When the sun angle is low, the sunlight intensity drops butthe likelihood of a glare incident increases. This is because thesunrays become nearly horizontal and can easily directly penetratedeeply into interior spaces. Spaces with windows facing directly east orwest are especially susceptible to this problem since they get a directsun exposure at very low sun angles, at sunrise and sunset,respectively.

The reduction of sun intensity early and late in the day can beexpressed as a sinusoidal function of the sun angle above horizonmultiplied by the atmospheric attenuation factor.

As is well known to those experienced in the art, based on the fact thatthe sun is substantially a point source, the sun illumination isEv=dF/dA=I*cos γ/r².

Where:

-   γ is the sun angle in respect to direction perpendicular to the    surface;-   I is luminous intensity;-   r is distance from the source;-   F is luminous flux;-   A is area.

Based on simple trigonometry it can be determined that the sunillumination on a horizontal task surface is a sinusoidal function ofthe sun angle above the horizon. The atmospheric attenuation factorvaries with pollution and moisture content of the air and these factorsalso affect the extent of perceived glare but can be neglected whendetermining how much the set point needs to be varied. Based onexperiments, it can be concluded that variation of the control set pointbased on the sun angle alone produces satisfactory glare controlperformance. The central processor 100 features an astronomic time clockso the sunrise and sunset times are available. The window treatmentprocess flow set point is therefore varied indirectly based on theastronomic time clock readings. In an average commercial building thecorrection is only required during a limited interval of timeapproximately three hours after sunrise and three hours before sunset. Aset point correction factor based on the sinusoidal function of thepredicted sun angle gives good practical results. The correction factorcan also be implemented in a digital system based on a lookup tabledirectly from the astronomic time clock reading.

For small sun angles, a linear approximation of the sinusoidal functioncan be applied, that is, since sin α˜α, where angle α measured betweenthe earth's surface and the sun's inclination above the surface.

According to the invention, two alternative methods for calculation ofset point correction to control interior illumination and glare aredescribed below. The symbols used are:

LSCF=low sun angle correction factor;

CTM=current time in minutes;

TSSTM=today's sunset time in minutes;

TSRTM=today's sunrise time in minutes;

CI=predefined correction interval after sunrise and before sunsetexpressed in minutes (CI is typically 120–180 min depending on thewindow height and proximity of furniture to windows);

NTSR=night time photosensor reading resulting from electric lights only;

NTUT=night time upper threshold derived from night time sensor reading(value influenced by electric lighting only)—by default this can be setto 20% above the NTSR;

NTLT=night time lower threshold—preferred value is 10% above NTSR toensure that window treatments remain open after sunset. Lower values maybe selected, for instance, to ensure that the window treatments remainclosed after sunset for privacy;

CUTHR=sun angle corrected upper threshold of the dead-band;

CLTHR=sun angle corrected lower threshold of the dead-band set point;

DTUT=upper threshold set point;

DTLT=lower threshold set point;

TARGET=target set point (preferably half way between LTHR and UTHR);

PSR=actual photosensor reading;

CPRS=corrected photosensor reading.

The following algorithm was successfully applied:

-   If (current time is within the predefined correction interval CI    before sunset)

LSCF=(TSSTM−CTM)/CI

-   Else if (current time is within the predefined correction interval    CI after sunrise)

LSCF=(CTM−TSRTM)/CI

-   Else

LSCF=1

-   CUTHR=(DTUT−NTUT)*LSCF+NTUT-   CLTHR=(DTLT−NTLT)*LSCF+NTLT

Alternatively the sensor (Photosensor) gain can be changed based onastronomic time clock readings to achieve an effect equivalent tolowering the thresholds:

-   If (current time is within the correction interval before sunset)

LSCF=(TSSTM−CTM)/CI

-   Else if (current time is within the correction interval after    sunrise)

LSCF=(CTM−TSRTM)/CI

-   Else

LSCF=1

-   CPSR=PSR*DTUT/((DTUT−NTUT)*LSCF+NTUT)

Based on the above, it can be seen that during the correction intervalafter sunrise and before sunset, a linear approximation of the suncorrection factor is made by dividing the time difference (in minutes)between sunrise (or sunset) and the current time during the correctioninterval by the correction interval. This results in a goodapproximation of the correction factor. This is illustrated in FIG. 14,which shows the two glare control intervals A (sunrise) and B (sunset).It can be seen that the target illumination is bounded by lines havingslopes. The instantaneous value of these lines represents the correctionfactor at a particular time during the glare control intervals. Notethat for the preferred embodiment, a correction interval of 180 minutesis used.

The default set point (before correction) is manually set duringcalibration based on the desired illumination in the space in front ofthe windows. Therefore the functions of illumination maintenance andglare control can be integrated in a single control algorithm. Thesevariable target illumination values are preferably set such that theyare, during the likely glare interval, below the sinusoidal curverepresenting the vertical daylight illumination variation on a clear dayand above the sinusoidal curve representing the variation of verticalillumination on a cloudy day. This allows the algorithm to differentiatebetween the clear sky condition and the overcast condition.

Based on the astronomic timeclock, the system at night timeautomatically detects and updates the component of the photosensor 145reading caused only by the electric lighting. This component ispreferably further subtracted from the daytime reading of the lightsensor to determine the component of the sensor signal caused only bydaylight.

Two alternative ways to correct for the decrease of illumination withthe sun angle which have essentially the same effect are thus describedabove. As discussed, since the incident illumination drops with the sunangle either the dead-band thresholds can be reduced for low sun anglesabove the horizon or alternatively the photosensor gain can be increasedand the midday dead-band thresholds maintained throughout the day.

FIGS. 10 and 11 show the process flow for the above sun angle correctionalgorithms. FIG. 10 shows one embodiment and FIG. 11 shows the abovedescribed alternative embodiment. Turning to FIG. 10, this figure showshow the system varies the dead-band set point or threshold in order toreduce glare, as described above. If the current time, as determined bythe astronomical time clock is either within the correction intervalbefore sunset (1300) or after sunrise (1310), the low sun correctionfunction is adjusted at 1320, 1330. If the time is not within thecorrection interval, the correction factor is set at 1 (1340). At 1350the dead-band thresholds are corrected by the correction factor. Thelight levels are then processed based on the new dead-band thresholds.

FIG. 11 shows the alternative embodiment where the photosensor gain isincreased. It is identical to the flow of FIG. 10, except step 1352 issubstituted for step 1350 of FIG. 11. At step 1352, the photosensorlight reading value is divided by the correction factor to increase thephotosensor value and the light reading, as corrected, is processed.Accordingly, in FIG. 10, the dead-band thresholds are adjusted and inFIG. 11, the potosensor readings are adjusted (by increasing them).

Since the window treatments must also be able to be controlled manually,the system must be able to account for manual overrides, i.e., when auser manually adjusts the window treatment. A manual override introducesa serious problem in a closed loop window treatment control system. Oncethe manual control command is executed, the interior illumination mayexceed the range defined by the dead-band of the control process flowand the system would automatically cancel the override. This obviouslyis undesirable. To address this problem, the process flow readjusts thecontrol set point after an override. Once the window treatments havestopped moving after a manual override, the process flow temporarilyadjusts the control set point to match the currently measured interiorlight level. The newly established light level is also preferably copiedinto another variable used to establish the long term preferences of theoccupants. During the low sun angle correction interval, previouslydescribed, the temporary override set point thresholds are corrected inexactly the same way as in the case where no manual override has beenapplied.

The temporary control set point can be canceled either based on thedaylight exceeding the bounds of the predefined dead-band established bythe temporary set point or based on a predefined time delay after anoverride or both. Once the override is canceled, the control systemreverts to the default set point.

The system can optionally adjust the default set point based on repeatedoccupant input. As stated above, each time an occupant performs a manualoverride, the newly established light level when the window treatmentsstop moving is further processed. The processing can be based onaveraging the override light level either continuously or based on thetime of day for instance only during the time interval when the sunglare is likely to occur. Once the long term average tendency isidentified, the system can make an adjustment of the default control setpoint to the usual or most likely user override.

FIG. 12 shows the process flow in the event of an override. At 1400 thesystem checks to determine if a manual override is currently applied. Ifso, at 1410 the system determines whether the shades are still moving asa consequence of the override. If yes, the system exits to return to themain loop. Once the shades stop moving, the system stores the currentlight level as a target set point for the control process at step 1420.At 1430, the system averages the override target level over time inorder to change the default set point based on occupant input and at1440 sets the flag to indicate that the setpoint has been manuallyoverridden.

If a manual override is not currently applied, as determined at 1400,the system checks at 1450 to determine if it is operating with amodified setpoint due to a previous manual override. If yes, the systemchecks at 1460 to determine if the modified upper or lower limit hasbeen exceeded. If no, the system exits to the main loop. If yes, at 1470the system determines if it is consistently overridden through a similaroverride set point. If yes, the system at 1480 modifies the defaulttarget light level toward the consistently used override level. If thesystem is not consistently overridden or after the modification at step1480, the system reverts at 1490 to the default setpoint for the targetlight level, clears the manual override flag and exits to the main loop.

FIGS. 13 a and 13 b shows the relationship between the sun angle and thedirect sun penetration into the space. FIG. 13 a shows how at low sunangles the direct sun rays penetrate deeper into the space and affectthe task surface basically representing a glare condition. FIG. 13 bshows the absence of direct incident sun rays on the task surfaceassociated with larger sun angles.

FIG. 14 graphically shows the daylight illumination variation of thevertical daylight illumination throughout a day for two conditions(clear and overcast), the variation of target illumination and the timeintervals A and B when glare control is needed and where the targetillumination is corrected to account for the reduction of illuminationcaused by the sun angle above the horizon.

Accordingly, the system described provides for the maintenance ofoptimal light levels in a space based upon optimal use of both daylightand artificial lighting provided by electric lamps. In addition, thesystem preferably automatically detects and reduces sun glare when sunglare presents a problem.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art.Therefore, the present invention should be limited not by the specificdisclosure herein, but only by the appended claims.

1. An illumination maintenance system for maintaining a desiredillumination profile in a space throughout at least a portion of a daywhere the illumination sources include daylight and artificial light,the system comprising: a first sensor for sensing an illumination levelin at least a portion of the space; at least one electricallycontrollable window treatment for at least one opening for allowingdaylight into the space, the window treatment selectively altering theamount of daylight entering the space through the opening; a pluralityof electric lamps providing artificial light to supplement the daylightillumination of the space, the electric lamps being dimmable and beingarranged in one or more zones in the space, the zones definingpredefined volumes of the space, each zone having at least one lamp; acontrol system controlling the at least one window treatment and theplurality of electric lamps to maintain the desired illumination profilein the space, the at least one lamp of each zone being controllable to adimming level to achieve a desired illumination level in the respectivezone according to the desired illumination profile; the control systemcontrolling the plurality of electric lamps so that the dimming level ofeach lamp is adjusted to achieve the desired illumination profile andcompensate for the daylight illumination in the space throughout atleast the portion of the day; and the control system further operatingto adjust the at least one window treatment in the event of sun glarethrough the opening to reduce the sun glare; wherein the dimming levelof each lamp is selected by the control system from one of a pluralityof lighting presets, each preset comprising a predetermined combinationof dimming levels of the at least one lamp in each zone and wherein thecontrol system adjusts the dimming level of the electric lamps toward alighting preset that will result in an appropriate supplementing of thedaylight illumination to achieve the desired illumination profile in thespace; and the control system operating such that when the desiredillumination profile within a predefined tolerance is achieved, thecontrol system stops varying the dimming levels of the lamps and theadjustment of the window treatment.
 2. The system of claim 1, whereinthe dimming level of each lamp is selected by the control system fromone of a plurality of lighting presets, each preset comprising acombination of dimming levels of the lamps and the control systemselects a preset that will result in an appropriate supplementing of thedaylight illumination to achieve the desired illumination profile in thespace.
 3. The system of claim 1, further comprising at least one secondsensor for sensing daylight illumination entering the space andproviding an input to the control system to control the at least onewindow treatment.
 4. The system of claim 3, wherein the at least onesecond sensor provides an input to the control system to control the atleast one window treatment to reduce sun glare.
 5. The system of claim1, wherein the at least one first sensor provides an input to thecontrol system to control the at least one window treatment and theplurality of electric lamps.
 6. The system of claim 1, furthercomprising a plurality of first sensors for sensing the illuminationlevel in the space.
 7. The system of claim 6, wherein a combined outputlevel of the first sensors is determined by averaging outputs of theplurality of first sensors.
 8. The system of claim 6, wherein thecontrol system employs a dead-band having upper and lower set pointssuch that if the sensed illumination in the space is outside thedead-band, the window treatment is adjusted to bring the illuminationlevel in the space within the dead-band.
 9. The system of claim 8,wherein the control system employs a time delay before moving the windowtreatment to bring the illumination level in the space back within thedead-band.
 10. The system of claim 9, wherein the time delay to bringthe illumination level in the space back within the dead-band is shorterfor high illumination levels than for low illumination levels.
 11. Thesystem of claim 10, wherein the timing delay is reduced if daylightillumination is consistently high or consistently low.
 12. The system ofclaim 8, wherein during a time period when glare from the sun throughthe opening can occur, at least one set point of the dead-band can bevaried to reduce glare.
 13. The system of claim 12, wherein a set pointis variable during a time period determined by an estimated angle of thesun.
 14. The system of claim 13, wherein the set point is reduced duringthe time period when glare from the sun through the opening can occur.15. The system of claim 13, wherein the set point is variable duringperiods approximately two hours after sunrise and two hours beforesunset.
 16. The system of claim 13, wherein the control system includesan astronomical time clock and the set point is calculated in responseto the time determined by the time clock.
 17. The system of claim 8,wherein a user can manually adjust the window treatment, and furtherwherein at least one of the set points is temporarily adjusted after amanual adjustment to match the light level measured after the manualadjustment.
 18. The system of claim 17, wherein the control systemreverts to a default set point after the light level exceeds apredefined dead-band around the temporary set point set after a manualadjustment.
 19. The system of claim 18, wherein the default set point isadjusted automatically after the control system detects a repeatedmanual adjustment of the window treatment.
 20. The system of claim 1,wherein the control system adjusts the window treatment to maximize theamount of daylight entering the space when the illumination leveldetected by said first sensor is too low.
 21. The system of claim 1,wherein the control system adjusts the window treatment to minimize theamount of daylight entering the space when the illumination leveldetected by said first sensor is too high.
 22. The system of claim 1,wherein the control system compares the illumination level in the spaceto first and second thresholds, the first threshold corresponding to alight level that is too dark and the second threshold corresponding to alight level that is too high.
 23. The system of claim 22, furtherwherein the control system has a main control loop in which theillumination level is compared to the first and second thresholds and afirst subloop to select an appropriate dimming level of the plurality ofelectric lamps when the light level is too dark and a second subloop toselect an appropriate dimming level of the plurality of electric lampswhen the light level is too high.
 24. The system of claim 23, whereinthe control system determines in the main control loop if the lightlevel is acceptable.
 25. The system of claim 23, wherein the dimminglevels comprise a plurality of preset dimming levels.
 26. The system ofclaim 1, wherein the control system adjusts the sensitivity of the firstsensor to compensate for the first sensor's differing sensitivity todifferent light sources.
 27. The system of claim 1, wherein the sensorhas a gain factor, and the control system adjusts the gain factor duringthe time period when glare from the sun through the opening can occur.28. The system of claim 1, wherein the control system includes anastronomical time clock, and wherein the time of day data provided bythe time clock is used to correct a spectral sensitivity property of thesensor.
 29. A method for maintaining a desired illumination profile in aspace throughout at least a portion of a day where the illuminationsources include daylight and artificial light, the method comprising:sensing an illumination level in at least a portion of the space;providing at least one electrically controllable window treatment for atleast one opening for allowing daylight into the space, the windowtreatment selectively altering the amount of daylight entering the spacethrough the opening; supplementing the daylight illumination of thespace with a plurality of electric lamps providing artificial light, theelectric lamps being dimmable and being arranged in one or more zones inthe space, the zones defining predefined volumes of the space, each zonehaving at least one lamp; controlling with a control system responsiveto the sensed illumination level the at least one window treatment andthe plurality of electric lamps to maintain the desired illuminationprofile in the space, the step of controlling comprising adjusting thedimming level of the at least one lamp of each zone to achieve a desiredillumination level in the respective zone according to the desiredillumination profile and thereby maintain the desired illuminationprofile in the space and compensate for the daylight illumination in thespace; controlling with the control system the plurality of electriclamps so that the dimming level of each lamp is adjusted to achieve thedesired illumination profile and compensate for the daylightillumination in the space throughout at least the portion of the day;further adjusting with the control system the at least one windowtreatment in the event of sun glare through the opening to reduce thesun glare; wherein the dimming level of each lamp is selected by thecontrol system from one of a plurality of lighting presets, each presetcomprising a predetermined combination of dimming levels of at least onelamp in each zone and wherein the control system adjusts the dimminglevel of the electric lamps toward a lighting preset that will result inan appropriate supplementing of the daylight illumination to achieve thedesired illumination profile in the space; stopping varying of thedimming levels of the lamps and the adjustment of the window treatmentwhen the desired illumination profile within a predefined tolerance isachieved; and repeating the above steps during the day to maintain thedesired illumination profile throughout at least the portion of the day.30. An illumination maintenance system for maintaining a desiredillumination profile in a space throughout at least a portion of a daywhere the illumination sources include daylight and artificial light,the system comprising: at least one interior sensor for sensing anillumination level in at least a portion of the space; at least oneelectrically controllable window treatment for at least one opening forallowing daylight into the space, the window treatment selectivelyaltering the amount of daylight entering the space through the opening;a plurality of electric lamps providing artificial light to supplementthe daylight illumination of the space, the electric lamps beingdimmable; a control system controlling the at least one window treatmentand the plurality of electric lamps to maintain the desired illuminationprofile in the space; the control system controlling the plurality ofelectric lamps so that the dimming level of each lamp is adjusted toachieve the desired illumination profile and compensate for the daylightillumination in the space throughout at least a portion of the day;wherein the control of the electric lamps is implemented based on anopen loop control algorithm and the control of the at least one windowtreatment is implemented based on a closed loop control algorithm; andwherein the control of both the electric lamps and the at least onewindow treatment is based on a signal representing a single inputvariable derived from the at least one interior sensor.
 31. The controlsystem of claim 30 wherein the at least one interior sensor is replacedby a plurality of interior sensors whose output signals are processed bythe control algorithms as a single input variable.